The ACLU said Tuesday that it had filed charges with the Equal Employment Opportunity Commission, the federal agency that overseas civil rights violations in the workplace, against Facebook and 10 other companies. The charges allege that Facebook’s online ad platform lets companies post job ads that are only shown to male users and not to females or those who don’t ascribe to a particular gender, in violation of the Civil Rights Act.

Organizations that are alleged to have posted discriminatory ads on Facebook include the auto repair company Rice Tire, business software firm Abas USA, window replacement company Renewal by Andersen, retail company Xenith, and the Greensboro, N.C. police department.

The ACLU said in a statement that “most of the employers’ male-targeted ads highlighted jobs in male-dominated fields.”

Although the charges emphasized sex and gender discrimination claims, they also alleged that employers could use Facebook’s ad system to post job ads that discriminate by age. The EEOC must now review the charges before a formal lawsuit can be filed.

Galen Sherwin, a senior staff attorney with the ACLU Women’s Rights Project, said that the ACLU and other civil rights organizations discovered that “gender discrimination was a major issue” on Facebook’s platform. One of the first things advertisers can choose to select when posting a job ad is whether they want to target males, females, or both, she said.

The ACLU discovered that the companies identified in the charges posted discriminatory job ads by clicking on a Facebook tool labeled “Why am I seeing this ad?” When a Facebook user plugged in some of the job postings and used the tool, they discovered that the ads only targeted men.

The class-action charges are similar to a previous complaint against Facebook that was filed in August by the Department of Housing and Urban Development. That complaint alleged that Facebook’s ad platform could be used to unfairly discriminate people by race, religion, and other criteria.

Shortly after, Facebook said that it would fix the problem by removing over 5,000 unspecified ad-targeting options that companies could use to discriminate against people based on factors like ethnicity or religion.

Considering those recent legal problems and a high-profile 2016 ProPublica article about discriminatory housing ads related to race on Facebook, Sherwin said that it’s “kind of astounding actually that the company has not taken action” to stop employers from targeting ads to a specific gender or by age group.

“You would think it would be low hanging fruit,” Sherwin explained. That said, Facebook “has been swift to try and address the other problems when approached.”

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Sherwin also said that Facebook would run afoul of the law by letting employers post job ads that discriminate against women by targeting “interests that are explicitly gendered.” For instance, a company that posted ads that exclude users who have an interest in “soccer moms” or “working moms” would still violate the law, she said. Sherwin also pointed to Facebook’s Lookalike Audiences tool that “allows employees to target ads based on what their existing customer base looks like” as another way companies could potentiality post discriminatory ads.

“There is no place for discrimination on Facebook; it’s strictly prohibited in our policies,” Facebook spokesperson Joe Osborne said. “We look forward to defending our practices once we have an opportunity to review the complaint.”

Abas USA called the charges “irresponsible and false.”

“We did not use targeted Facebook ads to exclude women,” the company said in a statement. “Just the opposite. We used a targeted ad in Facebook to specifically include women.”

Story updated at 7:45 AM PT to clarify that a Facebook user accessed the “Why am I seeing this ad?” tool.

Updated on Sep.19 at 5:00 PM PT with statement by Abas USA.